050 reject for in kernel

// TEST: raw control transforms are rejected inside kernel scope

~import std/kernel

~std/kernel:shape(Body) {
    mass: f64,
}

~std/kernel:init(Body) {
    { mass: 1.0 },
    { mass: 2.0 },
}
| kernel k |> for(0..2)
    | each _ |> std/kernel:self { k.mass *= 2.0 }